Surface grinding machine



0611. 24, H MYERS SURFACE GRlNDING MACHINE Filed may 9, i932 3 Sheets-Sheet l nvenfor H. L. MYERS oct. 24, 1933.

SURFACE GRINDING MACHINE Filed May 9, 1932 3 Sheets-Sheet 2 m w u Oct. 24, 1933. H. L. MYERS 1,932,319

SURFACE GRINDING MACHINE Filed May 9, 1932 3 vSheets-Shea?, 5

t Invenlor y Harry L. /M er@ llomey Patented Oct. 24, 1933 UNITED STATES c SURFACE GRINDING' MACHINE Harry L. Myers, Toledo, Ohio, as'signor to The American Floor Surfacing Machine Co., Toledo, Ohio, a' corporation of Ohio Application May 9, 1932. serial No. 610,188 19 claims. (C1. 51-177) This invention relates to surface grinding machines and has more specific reference to a comparatively small light weight portable type ma-y chine particularly designed for grinding and levelling terazzo oors, vmonolithic slabs and the like.

By way of introduction, it is to be related that this type of floor (terazzo work) is more or less uneven'as the result of rolling and trowelling and any attempt to grind the surface to the requisite evenness and smoothness requires the provision of a flexible, yet rigid and sturdy machine. Generally this class of Work is doneby a machine of the planetary type, that is, one including a rotary l5 head or adapter plate having marginal abrasive stones or blocks.

Delving into the prior art, it would be noticed that ordinarily these blocks are rigidly secured at equi-distant circumferentially spaced points toa rotary head or adapter plate( lIn order to cope with the uncertain surfacing conditions met in this particular line of endeavor, resiliently mounted Vheads are sometimesv used, that is, heads which are attached by a flexible coupling to the drive shaft, such as shown for example in prior Patents 1,142,570 and 1,537,279.

Despite the use of a flexibly mounted block equipped head and adapter plate and adjustable mountings for the blocks, disadvantages in grinding terazzo oors are still encountered. For eX- ample, where the blocks are attached to the underside of the adapter plate in a rigid manner, the outer edge portions thereof obviously travel faster or a greater number of feet per revolution than the inner edgeportions of the blocks or stones. Manifestly, this differential block abrading action causes the outer edge portions of the blocks or stones to wear away far more rapidly than the inner edge portions.

As a matter of fact when the surfacing stones are rigidly mounted on the adapter plate practically all of the cutting is done by the inner end of the stone, causing the stone to assume a tapered or wedge-shape such as promotes inefficient v grinding contact with the floor. One would think that eventually the stone would wearV down and get uniform Contact for a short period of time on the outer end portion. This, however, is not the fact when surfacing terazzo floors because it is the practice and generally 'necessary to spread bulk abrasive material on the floor during the grinding operation.

The abrasive isusually a fine grade of building sand and the object of distributing a fine film of sand over the oor is to permit the sand to serve as sharpening means for the abrasive stones. It has been observed that if the bulk sand or an equivalent abrasive is not used, the cutting action of the stones is materially reduced ,y whereas when the sand is employed it repeatedly sharpens the grinding surface of the stones at all times.

It is a matter of common knowledge to those skilled in this particular line of endeavor to notev that the loose sand has a tendency to pile up in front of the surfacing stones in the direction in which the stones are travelling. Naturally the centrifugal force tends to throw the sand to the outer end portions of the stone and after the outer end portion of the stone is gradually worn away and the stone becomes tapered, the sand gradually backs up under this portion of the stone and keeps breaking away the surfacing or abrading-face of the stone.

The purpose of the present invention is `to provide an appreciable contribution to the art and trade comprising a structure embodying the rotary adapter plate or head having the abrading stones so mounted on its marginal or peripheral portion as to compensate for Wear of the stones by insuring a substantially complete and oo nstant contact of the stones themselves with the surface being ground, irrespective of the irregularities or unevenness of the floor surface.

Stated otherwise, I have discovered the need '85 for abrasive stone mountings such as will function to rectify the errors of construction found in` prior art devices withA which I am familiar, the improved structure being designed to provide self-levelling of the abrading stones or blocks while in the actual grinding work in order to Ypro- Vide for more exacting performance and to pro.- mote uniform reduction in the Size .of .the ,Stones as they are ground away.

lAnumber of .other features and advantages ,of the invention herein illustrated and described will become more clearly evident from the .dis-.- closure.

Figure 1 is a view in section and elevation. 10U illustrating a small-sized terazzo grinding ma.- chineembodying the improved rockingty-pe sub.- plate orV stone` carrier. f

Figure 2 is a vtop plan view of the triple arm adapter or spiderplate detached from the drive shaft.

Figure 3 is a fragmentary elevational View Aof one of the rockable block carrier units.

Figure 4 is a section on the line 4 4 of Figure 2.

`Figure 5' is a View like Figure 2 showing the 110 gear casing or frame'is generally denoted by the numeral 9. The power driven gearing is generallydesignated by the numeral le, the guard is indicated at'11, and `the perpendicular-rotary drive shaft is denoted by the numeral 12.

The improved adapter plate Yis recognized by the numeral 13, this being attached to the drive flange or plate 14 through the medium of a flexible coupling 15, which is an arrangement covered in previous Patents 1,142,570, and 1,537,279. 1ncidently this structural ensemble serves to propel the adapter plate 13 and to render it substantially self-levelling to compensate for irregularitiesin the surface of the floor. No claim is made to this continuity of parts except'in combination with ^7the improved features of the invention now to be described. Y 1

Referring to Figure 5, it will be noticed that the adapter plate or head 13 is of a triplex spider type. It includes a body portion 16 and a plurality reof circumferentially spaced equi-distant radial arms 17. Inasmuch as each arm and associated abrading stone and mounting is the same, a description of one will suice for all. Therefore, as seenin Figure 6, the arm is formed in its under- -gside with longitudinally spaced spring accommodation sockets 18 and'formed on its top with a transverse pin orshaft bearing.

4The abrading stone or block, which is of oblong or longitudinally elongated rectangular con-l ijiiguration` is represented by the numeral 20 and detachably connected to the carrier or mounting unit 21. This comprises a backing plate 22 of appropriate dimensions and configuration having a sustaining flange 23 along one edge and a ^A jcentralized lug 24 on the opposite edge to accommodate the customary wedge (not shown) for holding the stone in place.

.In its top the backing plate is provided with sockets 25 `registering with the superposed sockets 5091313. The numerals 26 designate suspension ears through which thesupporting shaft or pin 27 (see Figures 3 and Ll) extends. The shaft is also mounted in the aforesaid bearing 19 and Vheld in place bya set screw 28. 4

557,, The numerals 29 and 30 designate coiled springs located in the aforesaid comple-mental sockets 18 and 25, the tension of these springs being regulated through the medium of feed screws 31 threaded. through appropriate openings 32 (see (5U-Figure 6) in the arm 17. Incidently, the numerals 33v designatelock nuts. In accordance with this arrangement, the block and its mounting are rockably mounted intermediate its ends and has adjustable spring means at equi-distant longitudinally spaced points on opposite sides of the pivot,

permitting. proper balance regulation.

It is to beiobserved in Figure 2 that the axis of oscillation of the block mounting is not at true right angles to the radial axis of the adapter plate. This'is purposely provided to permit the stones or blocks to be canted or offset with reeffects, first it produces a shearing action on the outer end portion of the stone; and secondly it serves to permit the stone to divert the sand and` water beneath the adapter plate due to the peculiar radial scraping and sweeping action.

Otherwise the centrifugal force would have a tendency to cause the stones to throw the sand and water out instead of scooping it in and under the adapter plate. 1

At this point in the description I wish to introduce the thought that certain prior art devices with which I am familiar comprehend the broad idea of tiltable abrasive blocks and stones, using universal joints or equivalent connections.. It has been observed, however, that in this type of radially tiltable stone, the stones have a tendency to wear off at both ends, leaving a convex or high portion in the center of the block when coming into contact with low spots in the iioor or vice versa, the stones will hop or jump, creating a chattering condition which is sometimes so severe that it will crack the abrasive blocks. VIn fact, it is common experience to find large portions of the blocks chipped off with 'the chips becoming jammed beneath the blocks leaving irreparable grooves and scratches in the floor. Y

By way of contrast the arrangement herein illustrated and described utilizes the variable equalizing spring pressureat opposite ends of the block with the pivot point of theY blocks located on a line corresponding to the path of travel, thereby providing the requisite rigidity and compensating for iiexibility. Moreover, the Vpliability of ther aforesaid iiexible coupling 15 for the adapter plate 13 affords a continuity of cooperation whereby the principal self -levelling condition is taken care of by the adapter plate itself, and wherein the spring-pressed tiltable abrasive stones afford an added'feature of accommodation and adaptation so necessary in permitting the stones to operate properly and travel in a true circular path.

The automatic spring resisted hinging action of the stones 20 co-operates witlrthe heavy pressure applied on the stones by way of the machine itself, permitting the stone to maintain a substantially complete fiat contact with the iioor. The tendency of the weight of the machine to maintain the 'stones `in flat contact with the floor naturally compresses the inner spring 30 and relieves the outer spring 29 of excessive tension.

By thus compressing the inner springs 30, these springs serve to exert a downward thrust on the inner end portions of the blocks 20 andeven though these inner ends travel slower than the outer ends, the pressure thus brought to bearV causes said inner ends to wear away a little faster than the outer ends which in turn keeps the grinding surfaces substantially flat to maintain uniform Contact at all times on the surface being To make this feature more effective, it is permissile-le to tension the inner spring 3i) to an even greater extent through the medium of the feed screws. Manifestly then, lthis differential spring pressure feature is a potent factor conserving the stone.

in conclusion it is tofbe pointed outV that where stones of this type are rigidly attached to the marginal portion of the adapter Vplate and no hinging action or spring balance introduced, when the outer end portions of the stoneswear away, it has been the practice to reverse the stones.v This practice however is detrimental in that only a portion of the stone comes into contact with the surface and frequently this portion is of such small dimension or area as to simply groove and not grind the iioor surface. l

The gist of the invention, it will be understood, is in the provision of a suitable supporting frame 9 and appropriate propulsion means 10 for the perpendicular rotary shaft l2; together with the adapter plate 13 and the flexible self-levelling driving coupling l5; in vconjunction with the hingedly mounted radially tiltable offset springpressed grinding stones and attachment means therefor assembled and operating in the manner heretofore described.

I claim:

l. In a structure of the class described, a rotary grinding head comprising an adapter plate embodying a plurality of radial arms, each arm being provided adjacent its outer end with a transverse bearing, a grinding block, attaching means for Y said block comprising a backing plate having quick releasable retaining means for the block, said backing plate and block being longitudinally elongated, a pair of oppositely disposed attaching ears carried by the longitudinal edge portions of said backing plate and straddling the adjacent edge portions of the arm, a 'shaft mounted in said bearings and cara-and coil springs interposed between the end portions of the backing plate and adjacent overlying portions of the arm.

2. In a structure of the class described, a rotary grinding head comprising an adapter plate embodying a plurality of radial arms, each arm being provided adjacent its outer fend with a transverse bearing, a grinding block, attaching means for said block comprising a backing plate having quick releasable retaining means for the block, said backing plate and block being longitudinally elongated, a pair of oppositely disposed attaching ears carried by the longitudinal edge portions of said backing plate and straddling the adjacent edge portions of the arm, a shaft mounted in said bearings and ears, coil springs interposed between the end portions of the backing plate and adjacent overlying portions of the arm, and feed screws carried by said arm for regulating the relative tension of the springs.

3. In a structure of the class described, a rotary adapter plate provided in itsunder side adjacent the marginal portion with inner and outer sockets, a transverse bearing located between the sockets, a backing plate including means for detachably connecting a grinding block therewith, the upper side of said backing plate being formed with sockets alined with said first-named sockets, ears attached to the longitudinal edge portions of said backing plate and disposed in alineinent with the end portions of the bearing, a pin mounted in the ears and bearing, and coil springs mounted in said sockets. 4

4. In a structure of the class described, a rotary adapter plate provided in its under side adjacent the marginal portion with inner and outer sockets, a transverse bearing located between the sockets, a backing plate including means for detachable connection of a Ygrinding block therewith, the upper side of said backing plate being formed with sockets alined with said first-named sockets, ears attached to the longitudinal edge portions of said backing plate and disposed in alinement with the end portions of the bearing, a pin mounted in the ears and bearing, coil springs mounted in said sockets, and regulating feed screws carried by the adapter plate and co-operable with the springs for regulating the relative tension thereof.

5. In a structure of the class described, a rotary grinding head, a grinding block, means for rockably mounting the grinding block at a point intermediate its ends on said head, and adjustable spring means associated With the head and end portions of the block to permit the inner end portion of the block to be forced yieldably and more firmly against the surface than the outer end portion thereof, whereby to insure uniform and even Wearing lof the block.

6,'A rotary adapter plate, a grinding block, attaching means therefor comprising a backing plate having rockable hinge connection with the adapter plate at a point intermediate the ends of the backing plate, and adjustable spring means associated with the plate and located on opposite sides of the hinge connection for the purposes stated.

7. A rotary adapter plate, a grinding block, attaching means therefor comprising a backing plate having oscillatory hinge connections with the adapter plate at a point intermediate the ends of the grinding block, adjustable spring means associated with the plate and located on opposite sides of the hinge connection for the purposes stated, the axis of oscillation of said hinge connection being slightly diagonal with respect to the path of rotation of the block to permit the block to function in diverting sand and water beneath the central portion of the adapter plate under the action of centrifugal force.

8. In a structure of the class described, a rotary adapter plate including a centralized body portion and a plurality of radial arms, said arms having substantially transverse bearings intermediate their ends, said bearings being disposed 110 at substantially diagonal angles to the circular path of` rotation of the arms, a pin supported in each bearing, a grinding block, a carrier therefor having hinge means connected with the pin to permit the block to tilt radially, and variable 115 spring means mounted on each arm and located on opposite sides of the'hinge pin to permit the pressure of the inner and louter end portions of the blocks to be regulated for the purposes specified.

9. A surface grinding machine of the class described comprising a driving head, a longitudinally elongated surface grinding block, oscillatory to permit the inner end portion of the block to be forced yieldably and more firmly against the surface than the outer end portion thereof, whereby to insure uniform reduction of the block and positive maintenance of the complete grinding face against the surface at all times.

10.`In a surface grinding machine of the class described, a rotary adapter plate, and a plurality of circumferentiallyspaced grinding blocks pivotallyl mounted kon Vhorizontal axes on the marginal portion of said plate, said blocks being radially elongated and a pivotal connection being diagonally disposed with respect to the path of movement of the blocks whereby to offset the position of said blocks in a manner to cast loose abrading material and Water beneath the central 145 portion ofthe adapter plate under the action of centrifugal `ffrce when the adapter plate is rotating.

`HARRY L. MYERS. 

